There has been known an energy storage device where terminals mounted on an outer portion of a container and current collectors disposed inside the container are connected to each other by conductive members. Connection strength between the terminals or the current collectors and the conductive members is ensured by welding the terminals or the current collectors and the conductive members to each other. See JP 2012-28246 A, for example.
When the terminal or the current collector and the conductive member are directly welded to each other, a swaged portion of the conductive member, that is, a bent portion of the conductive member is welded. In this case, a portion to be welded has an unstable shape and hence, there is a possibility that welding cannot be performed satisfactorily. When the weld turns out unstable, there is a concern that the connection between the terminal or the current collector and the conductive member is loosened due to vibrations or an impact. This loosening causes the increase of electric resistance so that the energy storage device cannot sufficiently exhibit energy storing performance.